1. Field of the Invention
This disclosure relates to devices and methods for surgery, and more particularly to volume restoration using injectable dermis.
2. Description of the Related Art
Cosmetic surgeons and the like commonly address contour defects and other volume abnormalities in soft tissues with various volume fillers. However, the volume fillers currently used for reconstructive and soft tissue augmentation all suffer from various drawbacks, many of which are discussed below.
For example, commercially available bovine collagen (derived from enzymatic degradation from bovine hides) lacks structural cross linking. Such collagen lasts as an implant for 4-6 weeks. There is also a concern over the possibility of transmission of Mad Cow Disease (“MCD”) using bovine collagen preparations. Human injectable collagen, derived from human fibroblasts in culture, is likewise enzymatically processed to remove cellular material. But due to the enzymatic nature of the process for rendering it injectable, there is significant loss of collagen cross linking and the product lasts a short period of time in the body. In the case of human collagen, there is also a small theoretical potential for viral transmission.
Restylane, a hyaluronic acid preparation, is FDA approved in the United States to augment the deep dermis and lasts 4-6 months. Drawbacks relating to Restylane include its cost per cubic centimeter (“cc”) and the need for multiple (3-6) cc's of volume filler in many clinical cases.
Autologous fat is also used for injection into the subcutaneous space and lasts 4-6 months. This method of subcutaneous filler augmentation requires a donor site harvesting procedure and involves over-correction at the insertion site, as there is considerable resorption of fat volume early on due to the destruction of damaged fat cells during the process. This leads to considerable short-term morbidity.
Hydroxyappetite crystals are FDA approved in solid block form for bone interposition grafting. This product is used off-label, and is injected subcutaneously to treat deep facial lines. Persistence of volume has been demonstrated for 12-14 months. Such material is not soft and is easily palpable in vivo and can cause granulomas if injected too superficially. It is not FDA approved for this use.
More permanent fillers such as Gore Tex are inserted as strips subcutaneously and can serve as a nidus for bacteria. Because they are solid sheets they do not allow for dispersion in the subcutaneous space and can cause visible sharp edges under the skin.
Medical grade silicone gel has historically been used as a filler but its use is currently condemned due to long term problems with granuloma formation and an unclear causal association with connective tissue diseases. Fragmented solid silicone microspheres are currently undergoing FDA evaluation for use in bulking the peri-urethral soft tissues in the treatment of urinary stress incontinence.
Internally placed autologous or allograft dermis enjoys existing use in the art for soft tissue structural reinforcement, providing structural stability and volume restoration to tissues subjected to atrophy or abnormal or physiological stress, such as the volume restoration treatment of hemifacial microsomia and the use in peri vesicular slings for urinary incontinence. Autologous dermis grafts have been demonstrated in the medical literature to survive in the body and establish a blood supply from the surrounding donor site, in a similar fashion that externally placed skin grafts do over open wounds. However, dermal sheet grafts are too bulky to be used beneath lines on the face and require access incisions to place. Although many cosmetic procedures involve the removal of excess skin, this skin, containing valuable autologous dermis, is most often discarded.
Despite the array of existing techniques and continued research and experimentation, current approaches have recognized drawbacks, including transience of volume filling, local reactions and undesirable donor sites. Therefore, there remains a need in the art for more satisfactory systems and methods for tissue volume filling and augmentation.